The desirability of enhancing the above cup aroma of soluble coffee has long been recognized. Focus has traditionally been on the aroma carrier, the substrate used to store and release aroma above the cup, and on the encapsulation of aroma.
One of the major problems associated with the current processes for manufacturing soluble coffee is the fact that the powdered product obtained lacks the desired aroma of freshly brewed coffee. This is the result of the loss and degradation of volatile aroma constituents, but also of the difference in the product matrices. Although the roasted coffee matrix is only partially soluble in water, soluble coffee powders and granules are readily soluble in water.
The aroma release from soluble coffee is poor because the aroma constituents are dispersed and locked in the fast dissolving soluble coffee glassy matrix. Due to this situation, the diffusion of the rehydrating liquid into the particle and the fast dissolution rate of the soluble coffee product will cause the majority of the aroma to end up in the brew. The typical aroma loadings of soluble coffee particles currently available on the market is from 50 μg/g to 400 μg/g, and because of the dissolution mechanisms highlighted above it is impossible to increase the aroma loading in the particles without adverse effects on the flavor.
Several food aromatizing compositions and preparation techniques have been attempted and disclosed by the industry over the last 30 years to overcome this problem.
In U.S. Pat. No. 3,989,852 Palmer prepares capsules by forming a viscid core medium, containing the aromatic constituents. This core is added to a film-forming agent which adheres to it and forms the capsule. The resulting capsule has a continuous structure, resulting in a slow dissolution rate and poor buoyancy. No particular attention is paid to the aromatic loading and characteristics. The practical application of this approach results in the encapsulation of aromatic substances, but sub-optimal release above cup upon reconstitution.
In U.S. Pat. No. 4,520,033 Tuot prepares capsules by using Palmer's procedure, but he also introduces an aeration step to facilitate buoyancy of the particles. The resulting capsules have a defined shell and an aerated core. Tuot claims that the aerated core also benefits aroma retention. It is not obvious to somebody skilled in the art that the voids in the core are beneficial to aroma retention. For example, Boskovic in U.S. Pat. No. 5,124,162 teaches the opposite. The patent contains some indications about coffee aroma compositions. In the body of the detailed description of the invention Tuot describes an aroma composition and loading in the capsules which are not optimal and will prevent the desired state from being achieved. Tuot in this same patent also introduces the benefits of coffee oil, a non-aromatic constituent of coffee, as a vehicle for storing and releasing aroma. This is a key feature in this art, since the use of oil will be systematically practiced in the following decades by different authors.
To this end, Garwood in WO 96/07333 discloses a process for encapsulating volatile aroma compounds, consisting of fixing the aromatics in coffee oil, gasifying this coffee oil and co-extruding it in a coffee melt. This reinstates the art of using coffee oil as the aroma fixative. The key drawbacks of this invention are: i) that the oil imparts unsightly oil slicks to the reconstituted coffee brews; ii) that as demonstrated in U.S. Pat. No. 6,544,576, coffee oil is characterized by a slow release rate, resulting in an imbalance in the aroma character.
Finally, Rushmore in U.S. Pat. No. 5,496,574 and Chmiel in U.S. Pat. No. 5,576,044 teach the benefits of hydrolysed coffee oil to overcome the unsightly oil slicks issue. Hydrolysed coffee oil, according to the author, has advantageous emulsifying properties and reduces the presence of large oil globules on the surface of the brew. The use of hydrolysed coffee oil as an emulsifying agent, mainly characterised for its fatty acids content, is not clear to somebody skilled in the art. Fatty acids themselves require emulsifying agents to be dispersed in water media. Furthermore, incorporating a material rich in free fatty acids into a beverage generally causes off flavours and accelerates staling due to the reactivity of the free acids (“Food oils and their uses” 2nd edition—T. Weiss—1983 the Avi Publishing Company”). Finally, if the aroma fixative is truly micro-emulsified in the brew, the droplets containing the aroma will be evenly distributed throughout the brew, rather than localised at the air/brew interface in a way which enhances above cup release.
An approach to provide heightened coffee preparation aroma might be to simply increase the amount of particles or capsules. The normal amount must be increased many times to produce a noticeable aroma and this approach results in a coffee beverage having an overwhelmingly strong taste and an unacceptable appearance.
In summary, the industry relies on combinations of coffee oil and coffee aroma, delivered using encapsulation techniques based on Palmer's 1975 invention or more recently based on co-extrusion. The major drawbacks of this approach are: i) unsightly oil slicks; ii) slow and unbalanced aroma release.
Most of the drawbacks presented by the described art were overcome by the teachings in U.S. Pat. No. 6,544,576 by replacing coffee oil with a novel generation of aroma carriers (volatile organic carriers). The new aroma carriers have beneficial release properties, enabling a fast and effective release of an aroma burst upon reconstitution of the instant beverage in water. The key features of this development can be described as follows.
A volatile coffee aroma is combined with a volatile, organic carrier to create a volatile coffee aroma composition which provides a good initial burst of coffee aroma at the time of preparation of a coffee beverage, while avoiding the problems noted above of residual surface oil and strong taste or aroma duing consumption. The use of a novel volatile carrier, having a combination of physical properties is key to this development and clearly distinguishes the aromatizing composi-tion from flavouring agents, either natural or artificial, which utilise traditional carriers. Traditional carriers are either too water-soluble, have a density greater than water, or are not sufficiently volatile to provide the preparation aroma impact desired while avoiding oily surface residues and potentially adverse effects on flavour. The volatile aromatizing composition is physically entrapped, preferably by encapsulating, in solid, water-soluble particles to reduce evaporation and oxidation during storage.
The use of those volatile organic carriers may provide several advantages. Since the volatile organic carrier is at most sparingly water-soluble, the carrier and aroma entrapped in the particle will be present as a separate liquid phase. This separate liquid phase in the particle is very important because it will prevent the rehydrating liquid from dissolving the majority of the aroma in the brew upon dissolution of the soluble coffee particle. Since the volatile carrier has a density less than the density of water, it will furthermore float to the surface of coffee beverages, where it can release aroma directly into the air above the beverage product at the time that it is prepared. This effect is desirable since it will serve to minimize incorporation of coffee aroma in the water phase by dissolution as described above, and to maximize the intensity of coffee aroma perceived by the consumer. Also, since volatile carriers rapidly evaporate along with the aroma, they do not leave behind an undesirable oil slick on the surface of the coffee beverage as occurs in applications that utilize non-volatile carriers such as coffee oil or other triglyceride oil.
In summary, to overcome the lack of aroma at the preparation stage, the coffee art has rarely focused on the quantity and quality of aroma constituents, but rather on the release vehicle and external constituents, like liquid carriers, to enhance release. The development described in the previous paragraph has perfected the approach using aroma carriers, and it is a significant improvement over the former art, however it still relies on an external ingredient, an aroma carrier, to deliver aroma.
There is still the need for an effective method for releasing aroma above a cup of coffee, which does not rely on the use of a carrier. In other words, the object of this invention is to provide aromatizing compositions which would, in their performance, match the advantages provided by the volatile organic carriers, and exceed the advantages of the coffee oil and aroma combinations, i.e., does not affect the appearance and the taste of the reconstituted product.